How to Make a Spot Welder - for Cheap!!

 by The King of Random
Contest WinnerFeatured
Spot Welder Thumbnail INSTRUCTABLES.jpg
 
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Step 1: You Might Be Surprised How Cheap It Can Be

Spot welder.jpg
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Have you seen the video above?  If not, take a look now because it will help you as you go along in this instructable. 

A typical resistance Spot-Welder can range in price from about $200-$800, but with a little resourcefulness, and a bit of free time, you can make one like this for about $10 or less.

Spot welders are used to fuse thin sheets of metal together.  They are most likely used in the auto industry, as well as HVAC for welding metal ducting.  

There are a couple of videos you should see before starting on this project, because you may want some background on how the device works.

Here is how to: Make The Metal Melter

Here is what it can do:  The Metal Melter
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f.masoni says: Apr 9, 2013. 7:06 AM
I love this project, i want to make one of my own but have a couple of questions.

Where i live the voltage of a power outlet is 220v does this change anything?

Also is it possible to make one that welds two separate spots at once with the same transformer.

Best Regards
calebwang says: Mar 9, 2013. 5:54 PM
I love your project. Your video editing is top notch as well.
The King of Random (author) in reply to calebwangMar 10, 2013. 5:20 PM
Thank you! Thank you!
micahamk says: Mar 9, 2013. 12:03 PM
Hi there. Thanks for this amazing project! I was amazed how easy it was to make. Luckily when I discovered this project, I knew were an old microwave was. I live in a small village in Guyana and most people here don't have microwaves. It was from a small restaurant. I successfully got the transformer out which was a little scary even for a 16 year old. I built a deluxe version of your design with the microwave light and fan incorporated in, along with four switches. My problem was that I didn't have any solid copper rod to use for the contacts. I had a few bronze welding rods so I used a small piece of that, instead. My welder is putting out about 1v. It melts nails and about anything else. I have not gotten it to actually weld. The metal to weld gets red hot but doesn't weld together. Any idea's whats wrong? I would appreciate any help. It's fun to melt metal, but it doesn't weld. Thanks.
The King of Random (author) in reply to micahamkMar 9, 2013. 2:35 PM
Thanks for your comment! I'd love to see a little video of your welder as a video response to my video on YouTube, if you get a chance to do that?

It may help to press the contacts together harder when welding. You may also need more power. (Eg. Bigger transformer)
swolff1234 says: Feb 25, 2013. 3:31 PM
Yes, I am actually a ham. I got my license in Jan. No radio yet, but I have Echolink. I am getting my radio in March. Are you a ham? Thanks for all your help! BTW, the reply feature isn't working for me, I can only post new comments.
--
Sam Wolff KK4NVJ
The King of Random (author) in reply to swolff1234Feb 27, 2013. 6:27 PM
Awesome! I did get licensed but haven't ever done anything with it. I'm hoping that one day I can explore that world a little more :)
swolff1234 says: Feb 24, 2013. 5:15 PM
Found it! It was hiding from me..... Lol. Thanks again! Oh, how long does the trasformer last until the insulation on the 4 awg melts?
Best of luck,
Sam

--
Sam Wolff
KK4NVJ
The King of Random (author) in reply to swolff1234Feb 24, 2013. 7:48 PM
Hey, are you a Ham by chance?

If you use the transformer in short bursts of 10 seconds or less, you should be able to use it indefinitely. Allow time to cool in-between. You'll be able to tell the wires are starting to melt because they will be smoking. So stop when you see smoke (or before) and it should last forever.
swolff1234 says: Feb 18, 2013. 2:25 PM
Thank you for the quick response. I have asked questions on other instructables on my old account about 3 years ago and still have not received an answer.
Do you remember what hardware store? I went to Home Depot and could not find it.
The King of Random (author) in reply to swolff1234Feb 18, 2013. 5:08 PM
It was Home Depot in the wire cutting area. All the best!
swolff1234 says: Feb 18, 2013. 2:44 PM
I also have a suggestion. When i built mine, I could not find a nail long enough for the pivot point. So I took a coat-hanger sized steel rod, and drilled a hole straight through the box and arm. I then bent the sides of the rod after I had fed the rod through the holes. I then found the nails. I compared the two pivot systems. I was amazed at how well mine worked.
The King of Random (author) in reply to swolff1234Feb 18, 2013. 5:07 PM
Excellent suggestion. Thank you!
swolff1234 says: Feb 17, 2013. 5:24 PM
First off, THANK YOU FOR THIS! I have been looking for something like this forever! Also, I don't have the solid copper wire, but I do have the same sized aluminum wire and I have stranded copper. Can I use the stranded and just twist it? And can i use the aluminum? Lastly, how much is the solid copper wire you are using and where can I get it?
The King of Random (author) in reply to swolff1234Feb 18, 2013. 8:28 AM
Thanks for asking. I got mine at the hardware store. They sell on rolls and you can buy it by the foot. Try to get 4 AWG solid copper wire. It's about $1.00 for 1 foot. The other wires you have can work, but it's going to be less effective.
jockywheel says: Jan 28, 2013. 2:42 AM
great design just check the 2x2 measurment. I have almost finnished mine cant wait to wire it up thanks for the easy to understand plans keep up the good work
The King of Random (author) in reply to jockywheelJan 28, 2013. 8:15 AM
You're welcome! I'm glad to hear you're having fun with your own project, and best of luck with it!
airbox1011 says: Jan 26, 2013. 8:52 PM
in my country it is hard to find solid copper to be used as electrodes, is it possible to use brass instead of copper
The King of Random (author) in reply to airbox1011Jan 27, 2013. 7:55 AM
I imagine those will work, but just not as well. Brass is an alloy of copper and zinc, and zinc has a much lower melting point (419.5 C). Copper is 1085 C so you'll probably have problems with your electrodes melting quickly. You can probably use it in small bursts, or find a way to keep the electrodes cool. That should help preserve them longer. Good luck!
airbox1011 says: Jan 26, 2013. 8:46 PM
i've made the spot weld similar to what was shown in the video using an 800 watts mot. my problem is when i tested it by joining two common nails or two galvanized iron wires it didn't joined together, the point of contact just turned into a red glowing and when it cools a white powder is produce.do galvanized iron wires can be spot welded? thanks for your help
Zephyr655 says: Jan 17, 2013. 5:49 PM
I did mean an induction heater. I have heard about the stick welder video you are making (which i know can be used to make a basic arc furnace) and was curious if something similar could be made with this.
jdtrd05 says: Jan 14, 2013. 12:54 PM
hi i made a spot welder the same way you explain is it normal the transformer make a loud noise and it dont melt it only making spark thank you
The King of Random (author) in reply to jdtrd05Jan 14, 2013. 2:14 PM
It is normal to hear a loud buzzing noise. Sparks should not be in the transformer, only on the ends of the cables.

I hope that helps!
jdtrd05 in reply to The King of RandomJan 17, 2013. 2:16 PM
thank you :)
Zephyr655 says: Jan 15, 2013. 3:00 PM
Is it at all possible to make this into some sort of furnace? Thank you.
The King of Random (author) in reply to Zephyr655Jan 16, 2013. 7:57 PM
Are you implying an induction heater? Or a furnace for heat in the winter?
kenk12 says: Jan 13, 2013. 8:26 PM
Great video! Thanks for taking time to record and share.
The King of Random (author) in reply to kenk12Jan 14, 2013. 9:17 AM
You're welcome. Thank you for taking time to appreciate and comment! :)
freazzer1 says: Jan 13, 2013. 10:28 AM
this is awesome!! i voted for you on both entries!!
I'm seriously thinking on making one of this.
The King of Random (author) in reply to freazzer1Jan 13, 2013. 3:29 PM
Thank you very much for your comment, and for your votes!!
Hubiewan says: Jan 11, 2013. 6:33 PM
Didn't see the wire guage of the heavy wire used for the transformer secondary, in the instructable. I'm seriously considering making one of these, with slight modification.
Hubiewan in reply to HubiewanJan 12, 2013. 11:56 AM
Thanks for your reply..............
The King of Random (author) in reply to HubiewanJan 12, 2013. 12:43 PM
You're welcome :)
The King of Random (author) in reply to HubiewanJan 12, 2013. 9:06 AM
It's 2AWG. Thanks for asking!
Energymadandy says: Jan 6, 2013. 4:47 PM
sir you are a genius!!!
thanks for the project,
I watched your videos a few times and got straight to work.
a few things to mention as help to others....
1) use the round holes in the corners of the laminate core to keep the laminates together when dismanling the core. a 6mm threaded rod and 2 bolts does the trick .
2) if you weld up the core when its wound and back together, shield the primary from the welding sparks.
3) one of your followers asked about the secondary coils size, non imp size is 16mm.
excellent project, i made mine in no time flat, i will be using it for every bit of tinkering I do in the future, (always soldered everything)
Thank you thank you thank you
The King of Random (author) in reply to EnergymadandyJan 7, 2013. 9:36 AM
I'm really glad you liked it, and thanks for your feedback. Did you weld your transformer back together? I'd like some info on how you did that?
Energymadandy in reply to The King of RandomJan 7, 2013. 12:21 PM
Jip ,the laminates are welded to begin with.
when i deconstructed the core, the laminates came unstuck so i used the threaded rod through the alignment holes in the corners to keep the whole lot together. so when it came to construction i had everything square. Clamped the whole lot in the bench vice and used my ac arc welder. Its an old brute and i cant get the amps low enough so using a 2mm rod burnt the core a bit. rather went for a 3mm which lowered the amps. i merely welded along the grinding wheel lines.
the spot welder, (or metal melter as it is now coz i got too inquisitive before finishing the welder) works great.

PS, on the subject of the old oil bath ac welder.
i want to start a bit of TIG welding and wondered if this would work....can i use a diode bridge rectifier to convert my ac arc welder into a dc welder and create a tig set up?????
here's where i saw it, http://www.weldingtipsandtricks.com/homemade-tig-welder.html can you shed any light on it for me?
thanks once again.
The King of Random (author) in reply to EnergymadandyJan 7, 2013. 2:25 PM
Thanks for the link.

I'm curious to know what you mean by the oil bath ac welder? I've actually been thinking about putting a transformer in an oil bath to help with the duty cycle on my stick welder.

Are there actually ac welders that do that?

Thanks for the updates on doing your weld on the transformer core. I'll have to give that a try.

As for rectifying the current, of course you can rectify the current, as long as you find diodes rated for that amount of current and heat sinks to help dissipate all the heat generated.

Thanks again for your feedback, comments, and best of luck!
Energymadandy in reply to The King of RandomJan 7, 2013. 8:26 PM
Hi again,
Jip the old oil bath welders use transformer oil to cool the windings.
I say old but they are still available (and produced in the thousands)
They are rather heavy so are mainly used at small factories or home. I just find that the welding current can't be set low enough for thin material.
DC inverters have taken over, being light and portable.

I notice on the video (welding tips and tricks) that the heat sinks are large aluminium channels that the diode bridge is built on. this should dissipate the heat accordingly, I would just use a lot more vanes when i build one.
another thing to think about (hint hint hint) is a way to reduce the welding amperage, so when using the TIG set up, i can weld very thin material.
I'm about to start building a chopper that has no transmission, or chain, belt or shaft drive...... so will be fabricating gas tanks, oil accumulators, etc. and need low amps for that. watch this space....
Just want to thank you again, magic talking to like-minded inventors.

The King of Random (author) in reply to EnergymadandyJan 8, 2013. 6:40 PM
I'm working on ideas to adjust amperage as well. Aside from buying an expensive variac.

I enjoy your comments. I don't have much experience welding personally, so I pick up ideas from your suggestions :)
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